Enclosed flare stack and method of flaring waste gas

ABSTRACT

An enclosed flare stack having expanded air entries for flaring waste gas. The flare stack includes an enclosure assembly having a bottom portion with expanded air entries and an upper portion through which the flared waste gas escapes. The enlarged air entries at the bottom end of the stack to reduce entry pressure loss and to increase entrained air flow when flaring waste gas. The enclosed flare stack and method of flaring waste gas also greatly reduce the height of the stack enclosure without greatly increasing the size of the flare windows.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application No.61/983,561 filed Apr. 24, 2014, the contents of which are herebyincorporated by reference

BACKGROUND OF THE INVENTION

This invention relates generally to an enclosed flare stack and methodof flaring waste gas, and more particularly to an enclosed flare stackhaving a series of enlarged air entries at a bottom end of the stack toreduce entry pressure loss and to increase entrained air flow whenflaring waste gas.

Flare systems are used in various industries to provide safe disposal offlammable liquids or gases. Flare systems are combustion mechanisms toburn off flammable liquids or gases. By way of example, flare systemsmay be used in industrial plants to burn off flammable gases released bypressure relief valves. Various types of flares exist, includingelevated flares and flares that operate near grade. Near-grade levelflares are often called ground flares.

Enclosed ground flares must be of a certain dimensions to maintain adesired combustion volume and a certain height to generate the requireddraft for combustion air flow. Large ground flares are often surroundedby a ground flare “fence” or “wall” that serves to reduce the amount oflight emitted by the flares. The fence also serves to limit the amountof infrared radiation from the flares, protecting personnel andequipment at grade. In addition, the fence serves to reduce the amountof noise from the flare by reflecting the noise. The fence must allowsufficient air flow through the fence to provide air flow forcombustion, and must also control the wind flow so that high winds donot interfere with flare operation.

One of the major costs of enclosed flares is the stack enclosure. Ashorter stack enclosure is less expensive, but entrains less air,whereas an enclosure with larger air entries, or “windows” can inducemore air through static draft for a given height, but in turn loses theability to direct the air flow at a given velocity magnitude and alsorequires a taller external radiation fence, both of which areundesirable.

It is therefore desirable to provide an enclosed flare stack and methodof flaring waste gas.

It is further desirable to provide an enclosed flare stack having aseries of enlarged air entries at a bottom end of the stack enclosure toreduce entry pressure loss and to increase entrained air flow whenflaring waste gas.

It is still further desirable to provide an enclosed flare stack andmethod of flaring waste gas that greatly reduce the height of the stackenclosure without greatly increasing the size of the flare windows.

It is yet further desirable to provide an enclosed flare stack having alower cost design by using about 25% less enclosure material compared tocurrent designs.

It is still yet further desirable to provide an enclosed flare stack andmethod of flaring waste gas that increase the available air flow to theflare system without increasing the line-of-sight to the high radiationflame zone.

It is still yet further desirable to provide an improved enclosed flarestack that is less visible from a distance and therefore has a lowerimpact to the surrounding community.

It is still yet further desirable to provide an enclosure assembly for aflare stack having angled air entries at a bottom of the enclosurewithout the need to increase the surrounding radiation fence of theflare stack.

It is still yet further desirable to provide an enclosed flare stack andmethod of flaring waste gas that have a low peak exit temperature fromthe flare stack.

It is still yet further desirable to provide an enclosed flare stack andmethod of flaring waste gas that have a relatively low impingingtemperature on the interior casing of the flare stack enclosure.

Other advantages and features will be apparent from the followingdescription, and from the claims.

SUMMARY OF THE INVENTION

In general, in a first aspect, the invention relates to an enclosedflare stack having a flow path for flaring waste gas. The stack includesan enclosure assembly having a bottom portion with at least one expandedair entry and an upper portion through which the flared waste gasescapes. The expanded air entry includes at least one upper panel havinga predetermined angle with respect to the upper portion of the enclosureassembly. The enclosed flare stack also includes a flare window adjacentto the expanded air entry of the enclosure assembly. The enclosed flarestack can also include a radiation fence that completely surrounds andcircumnavigates the flare stack. Flare manifold assemblies are in fluidcommunication with the flare windows, and may completely orsubstantially surround the flow path through the flare stack.

The predetermined angle between the upper panel of the expanded airentry and the upper portion of the enclosure assembly ranges betweenabout 110 to about 160 degrees, namely about 135 degrees. Thepredetermined angle between the upper panel of the expanded air entryand the upper portion of the enclosure assembly can also be a generallysmooth radius, downwardly sloping angle, or a concave angle toward theflow path through the enclosed flare stack. The expanded air entrycontinuously radially surrounds and enlarges the bottom portion of theenclosure assembly. The expanded air entry may be a plurality ofexpanded air entries. The expanded air entries can include side panels,open side windows or a combination thereof. In addition, the expandedair entries may be spaced from and generally parallel to each other orcontiguous with each other.

In general, in a second aspect, the invention relates to a method offlaring waste gas using an enclosed flare stack. The method includesflowing a waste gas through the enclosed flare stack; entraining airthrough at least one flare windows in the flare stack; entrainingadditional air through at least one expanded air entry having at leastone upper panel having a predetermined angle with respect to an upperportion of the flare stack; and flaring the waste gas. Similar to above,the expanded air entry may be a plurality of expanded air entries.Additionally, the predetermined angles between the upper panels of theexpanded air entries and the upper portion of the flare stack may rangebetween about 110 to about 160 degrees, be generally smooth radius,downwardly sloping angles, be concave angles toward the flow paththrough the enclosed flare stack or be a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example of an enclosure assemblyhaving a bottom with expanded air entries surrounded by a radiationfence in accordance with an illustrative embodiment of the enclosedflare stack and method of flaring waste gas disclosed herein.

FIG. 2 is a front plan view of the enclosure assembly shown in FIG. 1.

FIG. 3 is a cross-sectional view along line 3-3 of the an enclosureassembly shown in FIG. 2.

FIG. 4 is an exploded view of area 4 of the expanded air entry shown inFIG. 3.

FIG. 5 is a front perspective view of the bottom portion of theenclosure assembly in FIG. 2.

FIG. 6 is a front perspective view of an enclosure assembly havinganother example of expanded air entries in accordance with anillustrative embodiment of the enclosed flare stack and method offlaring waste gas disclosed herein.

FIG. 7 is a front perspective view of an enclosure assembly having stillanother example of expanded air entries in accordance with anillustrative embodiment of the enclosed flare stack and method offlaring waste gas disclosed herein.

FIG. 8 is a cross-sectional view along line 3-3 of the enclosureassembly shown in

FIG. 2 having yet another example of expanded air entries in accordancewith an illustrative embodiment of the enclosed flare stack and methodof flaring waste gas disclosed herein.

FIG. 9 is an exploded view of area 8 of the expanded air entry shown inFIG. 8.

FIG. 10 is a front perspective view of the enclosure assembly shown inFIG. 1 having yet another example of expanded air entries in accordancewith an illustrative embodiment of the enclosed flare stack and methodof flaring waste gas disclosed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatuses and methods discussed herein are merely illustrative ofspecific manners in which to make and use this invention and are not tobe interpreted as limiting in scope.

While the invention has been described with a certain degree ofparticularity, it is to be noted that many modifications may be made inthe construction and the arrangement of the structural and functiondetails disclosed herein without departing from the scope of theinvention. It is understood that the invention is not limited to theembodiments set forth herein for purposes of exemplification.

The description of the invention is intended to be read in connectionwith the accompanying drawings, which are to be considered part of theentire written description of this invention. In the description,relative terms such as “front,” “rear,” “lower,” “upper,” “horizontal,”“vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as wellas derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly”,etc.) should be construed to refer to the orientation as then describedor as shown in the drawings under discussion. These relative terms arefor convenience of description and do not require that the machine beconstructed or the method to be operated in a particular orientation.Terms, such as “connected,” “connecting,” “attached,” “attaching,”“join” and “joining”, are used interchangeably and refer to onestructure or surface being secured to another structure or surface orintegrally fabricated in one piece.

Referring to the figures of the drawings, wherein like numerals ofreference designate like elements throughout the several views, andinitially to FIGS. 1 through 3, an enclosed flare stack 10 havingexpanded air entries 12 for flaring waste gas. The flare stack 10includes an enclosure assembly 14 having a generally annular bottomportion 16 with the expanded air entries 12 and a generally cylindricalupper portion 18 through which the flared waste gas escapes. Asillustrated in the drawings, the upper portion 18 of the flare stack 10has a polygonal configuration, but is not so limited as other forms,such as a circle or oval, may be utilized. Moreover, the enclosureassembly 14 may form a single main flare stack having an open end 20 atthe upper portion as exemplified, or may have a closed end at the upperportion of the enclosure assembly with one or more radially extendingarm assemblies (not shown) in fluid communication with the main flarestack.

The enclosure assembly 14 may also include a plurality of structuralsupports 22 to position the bottom portion 16 of the flare stack 10 in aspaced relation from grade or ground level to form flare windows 24. Thestructural supports 22 may be fabricated from steel beams or othersturdy material, and may be secured at grade or ground level by concretefootings or the like. A radiation fence 26 completely surrounds andcircumnavigates the flare stack 10, and in general, the fence 26 has aheight generally equal to the height of the flare windows 24. A seriesof flare manifold assemblies 28 are positioned in the flare windows 24in fluid communication with a flow path 30 through the flare stack 10for flaring waste gas. Similar to the radiation fence 26, the manifoldassemblies 28 may completely or substantially surround the flow path 30through the flare stack 10. The manifold assemblies 28 may be arrangedin a wide variety of patterns and, depending on the application, themanifold assemblies 28 may be utilized simultaneously or at variousdifferent times.

As illustrated in FIGS. 1 through 5, the expanded air entries 12 may bemade by expanding the bottom portion 16 of the enclosure assembly 14immediately above the flare windows 24 to a larger area in order toincrease the rate of entrained air while flaring waste gas. The expandedair entries 12 may be constructed from steel and refractory orinsulation lining similar to the enclosure assembly 14. The expanded airentries 12 can be constructed from upper panels 32 having generallypredetermined angles A with respect to the upper portion 18 of theenclosure assembly 14. The upper panels 32 may be retained in place byhorizontal bracing 34, which can be generally parallel to grade and bycross bracing 36 extending between the horizontal bracing 34. Bracketsand/or other fasteners may be utilized to facilitate connections. Asillustrated for this example of the enclosed flare stack 10, thepredetermined angles A between the upper panels 32 of the expanded airentries 12 and the upper portion 18 of the flare stack 10 may range frombetween about 110 to about 160 degrees or generally about 135 degrees.The expanded air entries 12 may include side panels 38 that extendbetween the upper panels 32 and the horizontal bracing 34 to generallyenclose the expanded air entries 12. In this configuration, the sidepanels 38 are spaced from and generally parallel to each other onopposed sides of the expanded air entries 12. This arrangement of sidepanels 38 results in air flow space between adjacent expanded airentries 12. Alternatively, as shown in FIG. 6, the expanded air entries12 can have open side windows 40, which allow increased air intake toentrain with the flaring waste gas with minimal additional radiation. Byway of yet another example, as shown in FIG. 7, the upper panels 32extend between adjacent structural supports 22 with the expanded airentries 12 being contiguous with each other.

Turning now to FIGS. 8 through 10, the expanded air entries 12 areillustrated predetermined angles A forming generally smooth radius,downwardly sloping bell curves between the upper panels 32 and the upperportion 18 of the enclosure assembly 14 or concave angles toward theflow path 30 through the enclosed flare stack 10. The concave upperpanels 32 may be retained in place by horizontal bracing 34 and crossbracing 36, with suitable fasteners utilized to facilitate connections.The expanded air entries 12 may include side panels 38 or may includeopen side windows 40. Further, the expanded air entries 12 may be spacedfrom and generally parallel to each other or the expanded air entries 12may be contiguous with each other.

Whereas, the apparatuses and methods have been described in relation tothe drawings and claims, it should be understood that other and furthermodifications, apart from those shown or suggested herein, may be madewithin the scope of this invention.

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specificembodiments, it will be understood that this description is intended toillustrate and not limit the scope of the preceding description and theappended claims.

A first embodiment of the invention is an enclosed flare stack having aflow path for flaring waste gas, the stack comprising an enclosureassembly having a bottom portion with at least one expanded air entryand an upper portion through which the flared waste gas escapes, theexpanded air entry comprising at least one upper panel having apredetermined angle with respect to the upper portion of the enclosureassembly; and a flare window adjacent to the expanded air entry of theenclosure assembly. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph further comprising a radiation fence that completelysurrounds and circumnavigates the flare stack. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph further comprising aplurality of flare manifold assemblies in fluid communication with theflare windows. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph the manifold assemblies completely or substantiallysurround the flow path through the flare stack. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph wherein the predeterminedangle between the upper panel of the expanded air entry and the upperportion of the enclosure assembly ranges between about 110 and about 160degrees. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph wherein the predetermined angle is about 135 degrees. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph whereinthe predetermined angle between the upper panel of the expanded airentry and the upper portion of the enclosure assembly further comprisesa generally smooth radius, downwardly sloping angle. An embodiment ofthe invention is one, any or all of prior embodiments in this paragraphup through the first embodiment in this paragraph wherein thepredetermined angle between the upper panel of the expanded air entryand the upper portion of the enclosure assembly further comprises aconcave angle toward the flow path through the enclosed flare stack. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph whereinthe expanded air entry continuously radially surrounds and enlarges thebottom portion of the enclosure assembly. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thefirst embodiment in this paragraph wherein the expanded air entry is aplurality of expanded air entries. An embodiment of the invention isone, any or all of prior embodiments in this paragraph up through thefirst embodiment in this paragraph wherein the predetermined anglesbetween the upper panels of the expanded air entries and the upperportion of the enclosure assembly range between about 110 and about 160degrees, are generally smooth radius, downwardly sloping angles, areconcave angles toward the flow path through the enclosed flare stack orare a combination thereof. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the firstembodiment in this paragraph wherein the predetermined angle is about135 degrees. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph wherein the expanded air entries further side panels, sidewindows or a combination thereof. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the firstembodiment in this paragraph wherein the expanded air entries are spacedfrom and generally parallel to each other. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph wherein the air entriesare contiguous with each other.

A second embodiment of the invention is a method of flaring waste gasusing an enclosed flare stack, the method comprising the steps offlowing a waste gas through the enclosed flare stack; entraining airthrough at least one flare windows in the flare stack; entrainingadditional air through at least one expanded air entry in the flarestack, the expanded air entry comprising at least one upper panel havinga predetermined angle with respect to an upper portion of the flarestack; and flaring the waste gas. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the secondembodiment in this paragraph wherein the expanded air entry is aplurality of expanded air entries. An embodiment of the invention isone, any or all of prior embodiments in this paragraph up through thesecond embodiment in this paragraph wherein the predetermined anglesbetween the upper panels of the expanded air entries and the upperportion of the flare stack ranges between about 110 and about 160degrees, are generally smooth radius, downwardly sloping angles, areconcave angles toward the flow path through the enclosed flare stack orare a combination thereof. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the secondembodiment in this paragraph wherein the predetermined angle is about135 degrees. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the second embodiment in thisparagraph wherein the expanded air entries further side panels, sidewindows or a combination thereof

Without further elaboration, it is believed that using the precedingdescription that one skilled in the art can utilize the presentinvention to its fullest extent and easily ascertain the essentialcharacteristics of this invention, without departing from the spirit andscope thereof, to make various changes and modifications of theinvention and to adapt it to various usages and conditions. Thepreceding preferred specific embodiments are, therefore, to be construedas merely illustrative, and not limiting the remainder of the disclosurein any way whatsoever, and that it is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

1. An enclosed flare stack having a flow path for flaring waste gas,said stack comprising: an enclosure assembly having a bottom portionwith at least one expanded air entry and an upper portion through whichsaid flared waste gas escapes, said expanded air entry comprising atleast one upper panel having a predetermined angle with respect to saidupper portion of the enclosure assembly; and a flare window adjacent tosaid expanded air entry of said enclosure assembly.
 2. The enclosedflare stack of claim 1 further comprising a radiation fence thatcompletely surrounds and circumnavigates said flare stack.
 3. Theenclosed flare stack of claim 1 further comprising a plurality of flaremanifold assemblies in fluid communication with said flare windows. 4.The enclosed flare stack of claim 3 said manifold assemblies completelyor substantially surround said flow path through said flare stack. 5.The enclosed flare stack of claim 1 wherein said predetermined anglebetween said upper panel of said expanded air entry and said upperportion of said enclosure assembly ranges between about 110 and about160 degrees.
 6. The enclosed flare stack of claim 5 wherein saidpredetermined angle is about 135 degrees.
 7. The enclosed flare stack ofclaim 1 wherein said predetermined angle between said upper panel ofsaid expanded air entry and said upper portion of said enclosureassembly further comprises a generally smooth radius, downwardly slopingangle.
 8. The enclosed flare stack of claim 1 wherein said predeterminedangle between said upper panel of said expanded air entry and said upperportion of said enclosure assembly further comprises a concave angletoward said flow path through said enclosed flare stack.
 9. The enclosedflare stack of claim 1 wherein said expanded air entry continuouslyradially surrounds and enlarges said bottom portion of said enclosureassembly.
 10. The enclosed flare stack of claim 1 wherein said expandedair entry is a plurality of expanded air entries.
 11. The enclosed flarestack of claim 10 wherein said predetermined angles between said upperpanels of said expanded air entries and said upper portion of saidenclosure assembly range between about 110 and about 160 degrees, aregenerally smooth radius, downwardly sloping angles, are concave anglestoward said flow path through said enclosed flare stack or are acombination thereof.
 12. The enclosed flare stack of claim 11 whereinsaid predetermined angle is about 135 degrees.
 13. The enclosed flarestack of claim 10 wherein said expanded air entries further side panels,side windows or a combination thereof.
 14. The enclosed flare stack ofclaim 10 wherein said expanded air entries are spaced from and generallyparallel to each other.
 15. The enclosed flare stack of claim 10 whereinsaid air entries are contiguous with each other.
 16. A method of flaringwaste gas using an enclosed flare stack, said method comprising thesteps of: flowing a waste gas through said enclosed flare stack;entraining air through at least one flare windows in said flare stack;entraining additional air through at least one expanded air entry insaid flare stack, said expanded air entry comprising at least one upperpanel having a predetermined angle with respect to an upper portion ofsaid flare stack; and flaring said waste gas.
 17. The method of flaringwaste gas of claim 16 wherein said expanded air entry is a plurality ofexpanded air entries.
 18. The method of flaring waste gas of claim 17wherein said predetermined angles between said upper panels of saidexpanded air entries and said upper portion of said flare stack rangesbetween about 110 and about 160 degrees, are generally smooth radius,downwardly sloping angles, are concave angles toward said flow paththrough said enclosed flare stack or are a combination thereof.
 19. Themethod of flaring waste gas of claim 18 wherein said predetermined angleis about 135 degrees.
 20. The method of flaring waste gas of claim 17wherein said expanded air entries further side panels, side windows or acombination thereof.